Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount_t

On Tue, Mar 21, 2017 at 04:51:13PM -0700, Kees Cook wrote:

On Tue, Mar 21, 2017 at 2:23 PM, Eric Dumazet [off-list ref] wrote:

quoted

Unfortunately there is no good test simulating real-world workloads,
which are mostly using TCP flows.

Sure, but there has to be _something_ that can be used to test to
measure the effects. Without a meaningful test, it's weird to reject a
change for performance reasons.

This. How can you optimize if there's no way to actually measure
something?

quoted

Most synthetic tools you can find are not using epoll(), and very often
hit bottlenecks in other layers.


It looks like our suggestion to get kernel builds with atomic_inc()
being exactly an atomic_inc() is not even discussed or implemented.

So, FWIW, I originally tried to make this a CONFIG in the first couple
passes at getting a refcount defense. I would be fine with this, but I
was not able to convince Peter. :) However, things have evolved a lot
since then, so perhaps there are things do be done here.

Well, the argument was that unless there's a benchmark that shows it
cares, its all premature optimization.

Similarly, you wanted this enabled at all times because hardening.